(278d) Self-Assembled Biomimetic Multifunctional Coatings

The natural world is providing enormous inspiration for scientists to mimic the unique functionalities of biological systems for practical applications. Here we report a simple bio-inspired self-assembly technique for fabricating multifunctional optical coatings that mimic both unique functionalities of antireflective moth-eye and superhydrophobic cicada wings. Wafer-scale, non-close-packed colloidal crystals with remarkable large hexagonal domains are created by a spin-coating technology, which is based on shear-aligning colloidal silica particles suspended in non-volatile triacrylate monomers. The resulting polymer-embedded colloidal crystals exhibit highly ordered surface modulation and can be used directly as templates to cast poly(dimethylsiloxane) (PDMS) molds. Moth-eye antireflection coatings with adjustable reflectivity can then be molded against the PDMS master. The specular reflection of replicated nipple arrays matches the theoretical prediction using a thin-film multilayer model. The microstructures of the replicated films also lead to the formation of hydrophobic surfaces, even though the native material is inherently hydrophilic. These biomimetic materials may find important technological application in self-cleaning antireflection optical coatings and solar cells.